linux-kernel - Re: Regression in v4.0.0-rc1 with Android Binder

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Message-ID: <CAMP5XgdY6PHOD-QE-aePdME1XHw=aV1i=KyLcBv8WzJ_2UVoZQ@mail.gmail.com>
Date:	Thu, 26 Feb 2015 16:12:49 -0800
From:	Arve Hjønnevåg <arve@...roid.com>
To:	Amit Pundir <amit.pundir@...aro.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, a.ryabinin@...sung.com,
	dvyukov@...gle.com, kcc@...gle.com, dmitryc@...gle.com,
	adech.fo@...il.com, tetra2005@...il.com, koct9i@...il.com,
	sasha.levin@...cle.com, cl@...ux.com, iamjoonsoo.kim@....com,
	dave.hansen@...el.com, andi@...stfloor.org,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, penberg@...nel.org,
	David Rientjes <rientjes@...gle.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Riley Andrews <riandrews@...roid.com>,
	Serban Constantinescu <serban.constantinescu@....com>,
	John Stultz <john.stultz@...aro.org>,
	Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: Regression in v4.0.0-rc1 with Android Binder

On Thu, Feb 26, 2015 at 2:04 PM, Amit Pundir <amit.pundir@...aro.org> wrote:
> Hi,
>
> I ran into series of following binder mmap failures with v4.0.0-rc1:
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 1971 at mm/vmalloc.c:130
> vmap_page_range_noflush+0x119/0x144()
> CPU: 0 PID: 1971 Comm: healthd Not tainted 4.0.0-rc1-00399-g7da3fdc-dirty #157
> Hardware name: ARM-Versatile Express
> [<c001246d>] (unwind_backtrace) from [<c000f7f9>] (show_stack+0x11/0x14)
> [<c000f7f9>] (show_stack) from [<c049a221>] (dump_stack+0x59/0x7c)
> [<c049a221>] (dump_stack) from [<c001cf21>] (warn_slowpath_common+0x55/0x84)
> [<c001cf21>] (warn_slowpath_common) from [<c001cfe3>]
> (warn_slowpath_null+0x17/0x1c)
> [<c001cfe3>] (warn_slowpath_null) from [<c00c66c5>]
> (vmap_page_range_noflush+0x119/0x144)
> [<c00c66c5>] (vmap_page_range_noflush) from [<c00c716b>] (map_vm_area+0x27/0x48)
> [<c00c716b>] (map_vm_area) from [<c038ddaf>]
> (binder_update_page_range+0x12f/0x27c)
> [<c038ddaf>] (binder_update_page_range) from [<c038e857>]
> (binder_mmap+0xbf/0x1ac)
> [<c038e857>] (binder_mmap) from [<c00c2dc7>] (mmap_region+0x2eb/0x4d4)
> [<c00c2dc7>] (mmap_region) from [<c00c3197>] (do_mmap_pgoff+0x1e7/0x250)
> [<c00c3197>] (do_mmap_pgoff) from [<c00b35b5>] (vm_mmap_pgoff+0x45/0x60)
> [<c00b35b5>] (vm_mmap_pgoff) from [<c00c1f39>] (SyS_mmap_pgoff+0x5d/0x80)
> [<c00c1f39>] (SyS_mmap_pgoff) from [<c000ce81>] (ret_fast_syscall+0x1/0x5c)
> ---[ end trace 48c2c4b9a1349e54 ]---
> binder: 1982: binder_alloc_buf failed to map page at f0e00000 in kernel
> binder: binder_mmap: 1982 b6bde000-b6cdc000 alloc small buf failed -12
>
>
> Turned out that the following commit tripped off binder:
> ----------8<----------
> commit 71394fe50146202f2c8d92cf50f5ebc761acf254
> Author: Andrey Ryabinin <a.ryabinin@...sung.com>
> Date:   Fri Feb 13 14:40:03 2015 -0800
>
>     mm: vmalloc: add flag preventing guard hole allocation
> ---------->8----------
>
>
> Explicitly disabling the vmalloc no guard (VM_NO_GUARD) flag in binder
> worked fine for me. So does a fix like this look reasonable enough to
> submit?
> ----------8<----------
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -601,6 +601,7 @@ static int binder_update_page_range(struct
> binder_proc *proc, int allocate,
>                         goto err_alloc_page_failed;
>                 }
>                 tmp_area.addr = page_addr;
> +               tmp_area.flags &= ~VM_NO_GUARD;

This variable is not initialized, so I would expect this to add a
warning. Setting it to VM_NO_GUARD and removing, " + PAGE_SIZE /*
guard page? */" fromt he next line would be better. However, the "new"
map_kernel_range_noflush api seems like a better api to use for this,
since it removes the need to create a dummy vm_struct at all.

>                 tmp_area.size = PAGE_SIZE + PAGE_SIZE /* guard page? */;
>                 ret = map_vm_area(&tmp_area, PAGE_KERNEL, page);
>                 if (ret) {
> ---------->8----------
>
>
> Regards,
> Amit Pundir

-- 
Arve Hjønnevåg
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